Spray coating apparatus and method



Aug. 21, 1956 vJ. W. JUVINALL SPRAY COATING APPARATUS AND METHOD 2 Sheets-Sheet l Filed July 22, 1952 NVENTOR.

'JAMES w. JUVINALL f Blf/m,

Aug. 2l, 1956 J, w. JUVINALI.

SPRAY COATING APPARATUS AND METHOD 2 .Sheets-Sheet 2 Filed July 22, 1952 INVENTOR.

JAMES W. JUVINALL A fluor/ley' United States Patent O SPRAY coATING APPARATUS AND METHOD James W. Juvinall, Brendonwood,l Ind., assignor to RansburgElectro-Coating Corp., alcorporationof Indiana` Application VJuly 22, 1952Seral No. 300,213

11 Claims. (Cl. 2994-63) This application relates to spray coating apparatus and method, and more particularly to an electrostatic coating `arrangement provided with meansy forsubstantially instantaneously terminating coating discharge,l of a liquid material. The application is. a continuationy in part of my copending application Serial No. 257,501, liledNovember 21, 1951, now abandoned.

Electrostatic coating arrangements and systems have been heretofore developed and are known and used in the coatingfield, such arrangements being of aicharacter wherein the spray of liquidcoating material issuing from an-atomizing device is givenzan electric chargejatfthe time it leaves the spraying device or shortly thereafter, and deposition` of` the coating material particles isprimarily the result of electrostatic forces attracting. the particles to the surface of the article being'coated. This .is-.accomplished by creating an electrostatic field which includes the surface being coated and thecharged coating material particles moving generally toward-such articles. Coating arrangements of this character, wherein atomization takes place under the influence of electrostaticforces, have proved very satisfactoryl and extremely eflicient commercially in coating various types `of"articles,.particularly articles of such a character as to haveV beenconsidered. extremely diicult. or ineicient to spray coat before the. advent of electrostatic coating as relatively smallv articles, or articles with large open. spaces, as automobile steering wheels.

While atomization in such a coatingarrangement can be effected in a number of ways, itis often desirable that the liquid coating material be presentedfor atomization asan extended thin film since atomization is often eilicientlyelfected froml the'edge of such a lm; Various types ofv atomizing devices, commonly referred to as heads,'have been suggested for forming coating material into the desired lm. In` the copending applica,- tion of William W. Crouse, Serial No. 141,509, led January 31, 1950, there is disclosed and claimed both a straightv and a curved slotted blade as an atomizing head, capable of forming the coating material into a thin lm for atomization` therefrom. One of the most ellicient atomizing heads now used employes a rotating bell-like member with a flared inner surface communicating with an annular atomizing edge. When liquid coating material is supplied to the inner ared surface (as through a central passageway in thevbell-like member) the rotavtion effectsdistribution of the material in al substantially ing material, it is customary to supply a ow of liquid 70 coating material to the. head by useof a positive displacement pump. The accurate control of rate of delivery coating deposited on the article.

65 of'v coating dischargefrom the head.

2,759,763 Patented Aug. 211956 g ce possible with such a pump, in combination with such normally unvarying factors as the rate of movement of thearticle through the coatingzone and the area of surface being coated, enables close'control of the quantity of So long as atomization and coating movement of the particles can be continuous, the constant flow -of coating material to the head is desirable; but under some circumstances it is preferable to1 discontinue atomization'temporarily, as between relatively widely spaced objects on a conveyor, or when some adjustment or correction is to be made, or the like; While shuttingyoff the pump terminates continued ilow` ofvmaterialto `the head, it does not provide substantiallyinstantaneous termination. of' atomization. from heads of the character mentioned, as an` appreciable amount. of coatingmaterial which1is `present inthe iilm along the interior of the head or in the passageway leading to the atomizing zone at the edge, will continue-to move outwardly to the atomizing edge, although in a 2O constantly thinning and diminishing quantity, tocause a gradualipetering out of the coating discharge rather than alrelatively sudden termination thereof.

Inv manyl cases'. this relatively gradual discontinuance Vofcoating'discharge is undesirable, and I am here disclosingfand claiming an apparatus and method for subdownthe pump `or otherwise terminating theflow of coat'- ing materi'alto the head. I do this by providing a controll member adjacent the head, generally co-extensive with theV atomizing zone, and mounting it for movement between coating-terminating and coating-permitting: positions;4 with the control 'member in the lirst mentioned position=coactingfwith thehead in such a way astoeect termination of coating discharge therefrom, preferably without necessitating shutting down of the pump.

The foregoingand other features and advantages of 40 `this.inventionwill.be apparent from the following'specification and; thel drawings, in which:

Figure 1 isV alongitudinal vertical sectional view of anfatomizing unit of the character having a rotatingbell- 'likememberr with an annular edge providing the atomizing zone, the unit including coating terminating control meansy constituting one embodiment of my. invention, such means being illustrated in coating-permitting position;

Figure 2 isa view of the head shown' in Figure l, partly in side elevation and partly in vertical section,

showing the control-member in coating-terminating posiition;

Figure 3 is afragmentary sectional detail view along the line 3--3of1 Figure 1;

Figure 4 is an isometric view, partially broken away,

showing a slotted blade type of atomizing head which includes coating terminating control means constituting another embodiment of my invention, such means being shown in' coating permitting position;

FigureS is avsectional view of the head shown in Figure 4 showing the control member in coating-terminatingposition; and,

Figure 6 is a diagrammatic view ofone arrangement for permitting continuation of the flow of liquid coating material through the pump during periods ofl termination While two forms of means for controlling coating discharge are illustrated and will be described an embodiments ofmy invention, it will be understood that these are representative embodiments only; and it is to be further understoodthat further embodiments may be utilized without departing from the contemplated scope of the present invention, and that no limitations are to be implied from such specific description as shall now be provided.

Referring now more particularly to the particular ernbodiment of the invention illustrated in Figures l and 2, the atomizing unit or head only is illustrated, it being understood that the coating system as a whole would be of a type known and in use in the art. The arrangement as a whole will be described for convenience in understanding the present invention, but only briey, inasmuch as reference may be made to the aforementioned two copending applications for patents for more details, if desired. In general the article or articles being coated are moved on a conveyor, being grounded through the conveyor if they are conductive; and an electrostatic field is established between the articles and another electrode at or near the spray device, usually the atomizing head itself. Where atomization is effected electrostatically, the strength of the electrostatic field is made sufficient not only to effect movement of the particles to the article and deposition thereon, but also to effect atomization of the particles at the atomizing zone of the head, which would normally be supplied with a steady flow of liquid coating material by suitable supply means. In the majority of cases, the atomizing head would be spaced at least several inches and normally in the neighborhood of 8 or l0 inches from the surface of the articles being coated, and a potential would be used such as to provide a field gradient of the order of 10,000 volts per inch, the atomizing head usually being supported on suitable insulators and made the hot electrode.

The atomizing unit or head shown comprises a housing or body portion identified in general as 10, carrying a rotatable bell-like member 11 having an outwardly and forwardly ared inner surface 11a communicating with an annular edge 11b which provides the atomizing zone. The bell-like head member 11 is mounted on a hollow shaft 12 rotatably mounted in the body member 10 in suitable bearings, here indicated as 13 and 14. The means for rotating the shaft and bell-like member during operation is here shown as including a gear 15 on the shaft meshing with and driven by a worm 16 on the shaft 17 driven by any suitable means, as an insulated drive shaft. Near the back end (to the right as the parts are illustrated in the drawing) of shaft 12 is packing means for providing a fluid-tight seal between the rotating holloW shaft 12 and the body portion 10, this being here shown as comprising chevron packing members 18 urged into sealing engagement with their cooperating surfaces by a spring 19.

At the back end of the atomizing head (to the right in the drawing) is a chamber 20 communicating at one end with the interior of the hollow shaft 12 and at the other end with a connector nipple 21. In operation of the coating system, a hose connected to the nipple 21 would supply a flow of liquid coating material to the head, comprising part of a suitable supply arrangement normally also including a positive displacement pump and a reservoir of the liquid coating material. This liquid material would, during coating discharge from the head, flow through the chamber 20 and the interior of the hollow shaft 12 to the flared inner surface 11a of the bell-like member, spreading out radially in a film on this surface as a result of rotation of this member and moving to the atomizing zone at the edge 11b where atomization would be effected, the particles then moving to the surfaces of the articles being coated in accordance with a known method of operation.

The atomizing unit disclosed herewith now for the first time also includes a control arrangement for substantially instantaneously terminating coating discharge, and for rapidly re-initiating the coating operation when desired. In general, this comprises a control member 23 (preferably of a resilient or pliable material, as rubber or a suitable plastic) lying within the bell-like member 11, mounted on one end of a stem 24 which is at its other end coupled to motor means and valve means. The stem 24 is provided near its mid-point with a plurality of vanes, or spider members 24a, 24b and 24C, as may be best seen in Figure 3, having their ends received by and movable in cooperating grooves 12a, 12b and 12e in the inner surface of the hollow shaft 12, thus providing a drive connection between the rotating shaft 12 and the stern and control member carried thereby to insure synchronized rotation of these parts together while permitting relative longitudinal or axial movement of the control member. At the end remote from the control member the stem has xedly mounted thereon a spool 25 having its central reduced portion slidably and rotatably movable within an annular member 26 acting both as a part of the motor means and as a valve synchronized with operation thereof. The member 26, in the embodiment illustrated is of magnetic material and acts as the movable member of a solenoid motor having the coil or winding 2'7, the body portion 10a carrying the winding being of non-magnetic material. Where the head is at high potential, the solenoid motor shown would have to be energized and controlled by means insulated from ground in a manner suitable to the voltage applied to the head; or if desired, the solenoid motor illustrated may be replaced by an air motor comprising a piston and cylinder, the rubber hose of such an air motor providing the insulation in that case.

In the embodiment shown a spring 2S normally urges the member 26, and thus the stem and control member 23, to the position illustrated in Figure 1, this being the coating-permitting position. In this position it will be noted that liquid coating material entering through the connector nipple 21 of the head passes through the hollow shaft 12 to the inner surface 11a of the bell-like rotating head member, then out along this inner surface (through the space between it and the control member 23) to the annular edge providing the atomizing zone. The control member, as illustrated, has an annular portion generally conforming to and lying immediately within the inner surface of the bell-like member; the outer edge 23h of the control member being annular, concentric with and closely adjacent the inside of the bell-like member near the annular atomizing edge thereof, and the body portion 23a of the control member having its cooperating control surface fiared more sharply than the inner surface of the rotating head.

When it is desired briefly to terminate coating, energization of the winding 27 of the solenoid motor causes movement of the member 26 to the right as the parts are viewed in the drawing, the first portion of this movement being of a lost motion character and then engagement with the back shoulder 25a of the spool causing movement of the stem 24 and control member 23 to the right, again speaking with respect to the position of the parts as illustrated. The first portion of control member movement causes engagement between the annular outer portion of the control member and the inner surface of the rotating head closely behind the atomizing edge, blocking further movement of liquid toward said edge, only a very small film section existing beyond such initial point of engagement and the termination of coating discharge therefor being substantially instantially instantaneous. Meanwhile, movement of the combined motor and valve member 26 toward the right has uncovered (at a time previous to the coating-terminating connection, as a result of the lost motion connection), the re-circulation outlet 29, as may be best seen in Figure 2, this outlet preferably communicating with a hose leading back to the reservoir of the liquid coating material from which the pump draws. Accordingly, even though the pump continues operation and there is a continuance of ow of coating material to the head, there is a re-circulation by-pass arrangement thus provided which enables steady flow conditions to be maintained insofar as the pump and supply hose are concerned.

Because of the slight difference in angle'of are between the cooperative surfaces of the resilient or` pliable control member 23 andthe inside of the rotating head member l1, further movement of the control member to the right (toward the ultimate position illustrated in Figure 2), results in progressive engagement along the ared inner surface toward the central supply passageway, squeezing the material down into said supply passageway, this action occurring freely because of the open outlet passageway 2.9 during this movement, as is illustrated in Figure 2. This results in preventing any pile-up or accumulation of coating material on the inner surface of the bell-like member, so that when the solenoid winding is ydeenergized and the parts returned to the coating-permitting position illustrated in Figure l no large blobs or the like are discharged, but instead `a thin film again moves out toward and delivers coating material to the atomizing edge under satisfactory conditions for reinitiation of coating discharge therefrom.r

Referringnow to the embodiment illustrated in Figures 4 and 5, there1 is shown a slotted. blade type ofvatomizing head 4i),v which it is `understoodmay be employed in an eelctrostatic coating system. The particular head shown is largely in the form of a hollow blade and comprises twogenerally similar plates 41` and 42 preferably made of steel or other suitable rigid, machinable` material. The adjacent faces 41a and 42a of plates 41 and 42, respectively, are substantially smooth and flat. The outer surface along one edge each'of plates 41k and 42 (said edges being referred to herein .as leading edges) are concavely formed to make leading edges 41b and 42b quite thin and sharp.

Plates 41 and 42 are positioned'so that the leading edges41b and 42b are coplanar and form an extended narrow orifice 40a adjacent which atomization of the coating material may take place. The edges are uniformly separated from each other, as are faces 41a and 42a, by means of a shim 43'; of uniform thickness which extends along the three outer edges of plates 41 and 42. Shim 43, made of brass or other suitable material, may be from approximately 1/zto l0 mils or more in thickness, depending upon the type of liquid coating material being used and other factors. Shim 43 isv maintained in position by aseries of bolts- 44 extending through holes in the plate 42 and screwed into threadedaligned'holes in plate' 41.` Coating material'is fed into the head through a passageway 4S connected to la port 45a formed in plate 42 which leads into interior passage 46. This passage lies along the length of the head and lconnects with a narrow passageway 47 defined by faces 41a and 42a of the plates.

To effect substantially instantaneousv termination of coating discharge and .also rapid re-'initiation of the coating operation, a control arrangement for the head in accordance with my invention is provided. The coating controlmember, which may be made of eithera rigid or a flexible material, may be moved mechanically, by a solenoid motor, air pressure or other suitable means, from a first position'permitting flow of coating material through said orifice for atomization thereat to a second position preventing such-flow. In the embodiment shown, plate 4l contains a separate passageway 48 which runs from the outer face of the plate to a henri-'cylindrical port 49 xtending along the length of the head. Theaxiallopening of port 49 lying adjacent to face 41a'of the plate is closedby a exible diaphragm 50 which runs co-extensive with the atomizing zone of the headand whose outer surface, i. e., the surface of the diaphragm away from port 49, is ilushwith the surface of plate face 41a. The edges of the ydiaphragm are securely fastenedto plate 41 by a suitable binding material. The upper end of passageway 48 is connected by coupling 51 to an air hose 52 (shown only in Figure 6)- so that bysuitable controlsl air under pressure may be introduced into passageway 48 and port'49, th'us expanding diaphragm 50 andcaus- 6 ing itto move into coating-terminating positionby contact with face 42a as shown in Figure 5,

The coating control `arrangement shown in Figures 4 and 5 is preferably used in conjunction with apparatus for permitting uninterrupted ow of liquid coating material through the pump during periods of termination of coating discharge from the head and an embodiment of-such apparatus is shown diagrammatically in `Figure 6. A supply of liquid coating material is maintained in reservoir 53 and during periods of normal coating discharge the liquid is drawn through hose 54 by the action of positive displacement pump 55, thence continuing through hose 56 to head 40 for ilow to the atomizing edge of the head. When it is desired to temporarily but immediately terminate coating, air valve 57 is opened to permit air under high pressure to flow through air line 52 from air pressure tank 58 into passageway 48 and port 49. The air pressure is maintained so that in port 49 the pressure is substantially greater than the liquid pressure existing in narrow passageway 47 and, therefore, the air pressure will expand diaphragm Si) outwardly into passageway 47 and against face 42a, thus causing substantially instantaneous termination of the coating discharge.

Inorder to prevent the build up of an excessive liquid pressure in liquid hose S6, there may be provided a pump by-pass line 59, which during normal coatingdischarge is closed by a normally closed pressure valve 60 which will automatically open upon the liquid pressure in hose S6 rising to somewhat above normal operating pressure. Upon movement of diaphragm into coatingterminating position, the pressure of the liquid in hose 56 will rise until the operating pressure of valve 60 iS reached, in which case the valve will open to provideal path for re-circulation of the liquid :around pump 55. When diaphragm 50 is retracted into coating-permitting position, the drop in liquid pressure in hose 56 will cause valve to return to its normally closed position. Thus normal coating discharge may be resumed almost immediately upon the opening of diaphragm 50.

Atomization of coating material fed to the orifice 40a may be accomplished by connecting the head to a suitable source of electrical potential and maintaining an electrostatic potential differential between the head 40 and the article to be coated so as to direct the electrostatically atomized particles to the article to apply a coating thereon.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modiiications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

l. An electrostatic coating arrangement, including: an atomizing head having a bell-like portion providing an annular atomizing edge and a flared inner surface communicating therewith; means for supplying a flow of liquid material to said flared inner surface; means for rotating said bell-like portion for effecting distribution of a film of said material thereon and movement thereof to said `atomizing edge for electrostatic coating discharge therefrom; a control member having an annular portion concentric with and closely adjacent the inside of said annular atomizing edge and mounted for axial movement between coating-terminating position in engagement with the inner surface at least closely adjacent the Vatomizing edge and coating-permitting position spaced therefrom, and 'a motor in said head for moving said member between said positions, said motor being controllable from a point remote from said head.

2. An electrostatic coating arrangement, including: an atomizing head having a bell-like portion providing an annular atomizing edge and a iiared inner surface communicating therewith; means for supplying `a flow of liquid material to said iiared inner surface; means for rotating said bell-like portion for effecting distribution of -a film Iof said material thereon and movement thereof to said atomizing edge for electrostatic coating discharge therefrom; a control member with a resilient element having a portion generally conforming to and lying immediately within at least an outer section of said belllike head portion and mounted for axial movement between coming-terminating position in engagement with the inner surface at least closely adjacent the atomizing edge and coating-permitting position spaced therefrom; and a motor in said head for moving said member between said positions, said motor being controllable from a point remote from said 3. An electrostatic coating arrangement, including: an atomizing head having a bell-lilie portion providing an annular atomizing edge and a fiared inner surface communicating therewith; means for supplying a flow of liquid material to said fiared inner surface; means for rotating said bell-like portion for effecting distribution of a film of said material thereon and movement thereof to said atomizing edge for electrostatic coating discharge therefrom; a control member with a resilient element having a portion generally conforming to and lying immediately within at least an outer section of said bell-like head portion and mounted for axial movement between coating-terminating position in engagement with the inner surface of the bell-like head portion and a coating-permitting position spaced therefrom, movement to coatingterminating position being in a direction opposite to the direction of flow of said material, the resilient element surface being flared more sharply than the inner head surface with which it cooperates for causing coatingterminating engagement to first take place at a point closely adjacent the atomizing edge `and thereafter progressively along the flared inner surface of the bell-like head portion; and a motor in said head for moving said member between said positions, said motor being controllable from a point remote from said head.

4. An electrostatic coating arrangement, including: an atomizing head having a bell-like portion providing an annular atomizing edge and a fiared inner surface communicating therewith; means for supplying a flow of liquid material to said flared inner surface; means for rotating said bell-like portion for effecting distribution of a liim of said material thereon and movement thereof to said atomizing edge for electrostatic coating discharge therefrom; a control member with a resilient element having `a portion generally conforming to and lying immediately within at least an outer section of said belllike head portion and mounted for axial movement between coating-terminating position in engagement with the inner surface at least closely adjacent the `atomizing edge and coating-permitting position spaced therefrom; motor in said head for moving said member between said positions, said motor being controllable from a point remote from said head; and a by-pass valve synchronized with movement of said control member permitting continued liow of said liquid material when the control member is in coating-terminating position.

5. ln the atomizing head of an electrostatic coating arrangement wherein the head has a bell-like portion providing an elongated annular atomizing edge with a fiared inner surface communicating therewith for delivery thereto of liquid coating material supplied in a flow to the head, coating control means comprising: a control member having a resilient portion generally conforming to and lying immediately within at least an outer section of said bell-like head portion and mounted for axial movement between coating-terminating position in engagement with the inner surface at least closely adjacent the atomizing edge and coating-permitting position spaced therefrom; and a motor in said head for moving said member between said positions, said motor being controllable from a point remote from said head.

6. in the atom g head of an electrostatic coating arrangement wherein the head has a bell-like portion providing an elongated annular atomizing edge with a flared inner surface communicating therewith for delivery thereto of liquid coating material supplied in a flow to the head, coating control means comprising: a control member having a resilient portion generally conforming to and lying immediately within at least an outer section of said bell-like head portion and mounted for axial movement between coating-terminating position in engagement with the inner surface of the bell-like head portion and a coating-permitting position spaced therefrom, the resilient element surface being flared more sharply than the inner head surface with which it cooperates for causing coating-terminating engagement to first take place at a point closely adjacent the atomizing edge and thereafter progressively along the flared inner surface of the bell-like head portion; and a motor in said head for moving said member between said positions, said motor being controllable from a point remote from said head.

7. A method for controlling coating in an electrostatic coating arrangement having an atomizing head with a bell-like portion providing an annular electrostatic atomizing edge and a flared inner surface communicating therewith for delivering liquid coating material thereto upon rotation of said bell-like portion comprising terminating coating discharge from said edge by moving a resilient circular element into flow-terminating engagement with the interior of the bell-like head portion and effecting said engagement first closely adjacent the atomizing edge and thereafter progressively along the flared inner surface of the bell-like head portion.

8. An electrostatic coating arrangement of the character described, including: an atomizing head for effecting coating discharge of a liquid material from an atomizing zone; a first passageway leading from a source of liquid material to said atomizing head; means for supplying a continuous flow of said liquid material to said first passageway; a second passageway for providing a path of flow from said first passageway to the atomizing zone of said head; an alternative passageway for providing an alternative path of fiow from said first passageway for subsequent resupply to said first passageway; a first valve controlling the flow through said second passageway to said atomizing zone; and a second valve controlling the alternative resupply passageway from said first passageway, said two valves operating cooperatively and automatically for selectively varying the flow of said liquid material between said second passageway and the alternative resupply passageway.

9. An electrostatic coating head comprising means on the head defining an arrow linearly elongated slot-like passage means terminating in an elongated linear orifice, a control diaphragm positioned in said passage means adjacent to the orifice and extending substantially coextensively therewith and normally positioned to permit flow of coating material through the passage means, a passageway in the head and connected to the diaphragm, and means for supplying fiuid under pressure to said passageway to inflate the diaphragm to prevent flow of coating material through the passage means to the orifice.

l0. A method for controlling coating in an electrostatic coating arrangement having an atomizing head with an extended atomizing edge as the forwardmost portion of said head and an extended flow-guiding surface communieating therewith for delivering a thin film of liquid coating material thereto comprising maintaining the liquid film adjacent said atomizing edge at an electrical potential of suicient strength to be capable of electrostatically atomizing liquid coating material, and abruptly and completely terminating coating discharge from said atomizing edge by abruptly moving a movable element coextensive with said atomizing edge into flow-terminating, sealing engagement with said flow-guiding surface along the entire extent of said flow-guiding surface transverse to the direction of flow of the thin film of liquid coating material and rearwardly of and closely adjacent to said atomizing edge.

11. An electrostatic coating arrangement, including: an atomizing head having an elongated atomizing edge and an extended How-guiding surface communicating therewith; means for supplying a ow of liquid material to said ow-guiding surface for forming the liquid material into a thin film owing over said flow-guiding surface to the atomizing edge of said atomizing head; means for connecting said head to a high Voltage electrical circuit for making the lm of liquid coating material adjacent said edge one terminus of an electrostatic field of sufficient strength to be capable of electrostatically atomizing liquid coating material; a control member lying entirely rearwardly of said atomizing edge and having an extended portion coextensive with said how-guiding surface, said control member being mounted for movement between coating-terminating position in sealing engagement with said flow-guiding surface at least closely adjacent the 10 atomizing edge and coating-permitting position spaced therefrom; and means within said head for abruptly moving said control member between its two positions.

References Cited in the le of this patent UNITED STATES PATENTS 

11. AN ELECTROSTATIC COATING ARRANGEMENT, INCLUDING: AN ATOMIZING HEAD HAVING AN ELONGATED ATOMIZING EDGE AND AN EXTENDED FLOW-GUIDING SURFACE COMMUNICATING THEREWITH; MEANS FOR SUPPLYING A FLOW OF FLUID MATERIAL TO SAID FLOW-GUIDING SURFACE FOR FORMING THE LIQUID MATERIAL INTO A THIN FILM FLOWING OVER SAID FLOW-GUIDING SURFACE TO THE ATOMIZING EDGE OF SAID ATOMIZING HEAD; MEANS FOR CONNECTING SAID HEAD TO A HIGH VOLTAGE ELECTRICAL CIRCUIT FOR MAKING THE FILM OF LIQUID COATING MATERIAL ADJACENT SAID EDGE ONE TERMINUS OF AN ELECTROSTATIC FIELD OF SUFFICIENT STRENGTH TO BE CAPABLE OF ELECTROSTATICALLY ATOMIZING LIQUID COATING MATERIAL; A CONTROL MEMBER LYING ENTIRELY REARWARDLY OF SAID ATOMIZING EDGE AND HAVING AN EXTENDED PORTION COEXTENSIVE WITH SAID FLOW-GUIDING SURFACE, SAID CONTROL MEMBER BEING MOUNTED FOR MOVEMENT BETWEEN COATING-TERMINATING POSITION IN SEALING ENGAGEMENT WITH SAID FLOW-GUIDING SURFACE AT LEAST CLOSELY ADJACENT THE ATOMIZING EDGE AND COATING-PERMITTING POSITION SPACED THEREFROM; AND MEANS WITHIN SAID HEAD FOR ABRUPTLY MOVING SAID CONTROL MEMBER BETWEEN ITS TWO POSITIONS. 